Some animals, such as dogs, are well known for their powerful senses, which can detect many things in the environment that humans cannot. Along with the fact that they respond very well to training, people have found all sorts of uses for them, whether it be sniffing out drugs, explosives, or many other things. But a more recent and very exciting area of research using animals is disease detection, or more specifically, cancer detection. Dogs are far from the only promising animals in this area. Here are ten animals that might actually sniff out cancer in humans.
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In 2021, researchers in Korea published a paper showing that trained rats could detect toluene, an odor-producing liquid that can indicate the presence of lung cancer. You might be wondering how rats can communicate exactly what they can smell to people, and this is actually a bit strange: The researchers trained rats to jump onto a floating ledge whenever they could smell toluene.
To make the study more realistic, the rats were not simply presented with samples of toluene among a sequence of other odors. They were presented with actual human breath samples, which were collected by humans breathing into plastic bags and then sealed. Some of these samples were later spiked with toluene by the scientists. After more than 1,000 tests, the rats were about 82% accurate in detecting toluene.
It’s not just mammals that can help humans detect deadly diseases; the insects are also getting in on the act. Bees are reported to possess such a strong sense of smell that they can detect even a few molecules of a substance in a room, and have already been used to detect diseases such as tuberculosis and diabetes.
Also, they can be trained much faster than animals like dogs. Their antennae allow them to more accurately detect specific odors among a mixture of simultaneous odors, as would be the case with human breath samples. Susana Soares, a Portuguese product designer, was studying for her master’s degree when she developed an elegant glass device known as “Bee’s”, which allows people to breathe safely in a chamber containing bees, which have been trained with a sugar reward for answering. to the detection of certain chemical substances.
In a rather peculiar, if not downright bizarre experiment, researchers in the US decided to test whether pigeons could detect breast cancer from images. Surprisingly, they were able to do it just as well as humans! And they did it despite having a brain the size of a fingertip. However, their brains are quite powerful, particularly when it comes to images. It has been shown that they can remember up to 1,800 images and can distinguish between people, facial expressions and even letters of the alphabet.
The pigeons in the cancer study were trained to distinguish microscope images of cancerous and non-cancerous tissue, and were rewarded for giving correct answers. When presented with invisible images, they were able to apply what they had learned and correctly distinguish between images, even when the images were zoomed in or out or washed out. It is believed that the pigeons could help validate future imaging-based cancer detection methods.
Ants, like bees, have very sensitive antennae that allow them to detect all kinds of substances that escape human senses. As we now know, specific chemicals released by cancerous tumors can have distinctive odors. However, the breath is not the only bodily emission in which these chemicals can appear. The compounds also show up in urine, and in 2023, scientists discovered that ants were highly accurate in detecting these compounds in the urine of mice.
It is believed that ants could offer a cheaper and less invasive way to detect cancer early. But how are ants trained to respond to the presence of chemicals? Like the other animals on this list, they were trained with rewards. In this case, it was sugar water. When the researchers stopped giving them the sugar water, the ants lingered a little longer in the presence of the urine samples with the cancerous compounds because they expected their reward.
Well, man’s furry best friend had to be on this list somewhere. With a sense of smell estimated to be 10,000 to 100,000 times better than ours, it probably comes as no surprise that dogs can sniff out cancer, too. Dogs can detect cancer in expelled matter such as breath and urine, just like the ants and bees mentioned earlier on this list. Plus, they can even detect cancer while it’s still in situ, meaning it hasn’t spread from the original site where it started.
This is great news as early detection is crucial because cancer is much more difficult to treat once it has spread. The dogs have been trained to detect cancer in breath, plasma, urine and saliva, and around 300 samples are needed to train them before they can learn the scent and apply it to new, invisible samples. While some organizations use canines to detect cancer directly, other researchers are looking at their abilities to help build a mechanical nose that will be able to detect cancer in the same way while letting dogs go about their day.
5 fruit flies
It may surprise you to learn that fruit flies actually possess less than half the number of odor-sensitive receptors that bees do. So why use them? Well, possibly because they can communicate much more clearly than bees, as researchers in Germany and Italy have found. In fact, scientists managed to genetically modify the flies so that they glow when they sense the presence of particular chemicals.
In this study, flies were blown with air containing the scent of breast cancer cells and healthy respiratory tissue. The scientists then looked through a microscope for flickering fluorescent patterns on the flies’ antennae as they detected the scents. Apparently, fruit flies have a base genome that lends itself to modification, which means that altering their genes is quite easy. Add to this that they are cheap to breed and still possess very sensitive olfactory receptors. They once again offer a promising solution to the crucial problem of early detection of cancer.
The worms in this research are common roundworms that, at a minuscule 1mm long, are much smaller than the slime-eating worms you find in your garden. Roundworms may be less interested in mud, but they seem to be very interested in cancer cells, especially when they’re hungry. In the experiment, Korean scientists placed about 50 worms on microscope slides, along with healthy human cells and cancer cells. About 70% of the worms made their way into cancer cells.
While it’s unknown why cancer cells constantly attract worms, scientists have a theory: Cancer cells emit many of the same odor molecules as rotten apples, something we all know is attractive to other worm species. The next step is to see if they can detect cancer when presented with substances such as urine or breath rather than being presented directly with cancer cells.
Like fruit flies, locusts are something of a scientific staple; scientists already know a lot about their features and even how their brains are wired. When it turned out that they also possess a powerful sense of smell, it was only natural to study their use in detecting disease, though not before they had been tested to detect explosives. However, the researchers did not train these very creepy critters to respond to cancer cells. Instead, they attached electrodes to the lobsters’ brains to see how they responded to the gases produced by the cancerous and healthy cells.
In fact, it turns out that lobsters could do more than just make a binary distinction between healthy and cancerous cells. In fact, they were able to differentiate between three types of cancer. As impressive as that may be, you might be relieved to hear that scientists plan to replicate the biology that allows for such highly sensitive detection and don’t intend for doctors to test patients with live lobsters.
This is where science begins to give way to speculation, although cats have surprisingly good noses. Although not as powerful as a dog’s, cats’ noses are significantly larger than humans’, and it is believed that they can actually differentiate scents better than dogs and humans. There is certainly some promise there, although no scientific studies have been done yet. However, there are some interesting anecdotes.
In 2010, a Franklin, Tennessee woman visited her doctor after a mysterious bruise appeared on her chest from a spot where her cat had been continuously kicking and jumping the night before. She found out it was breast cancer. A year earlier, a story made headlines in Canada in which a Calgary man testified that his cat had alerted him to her lung cancer with her persistent pawing at his owner’s left side. The owner credits his cat, Tiger, who was apparently not very affectionate previously, with saving his life.
It’s clear from the many studies listed above that cancers have specific odors, which raises the question of whether humans can detect them as well. Of course, our noses are not as powerful as those of many other animals, especially dogs. However, a super smelly nurse from Scotland thinks it’s possible some people smell cancer.
Joy Milne, a former nurse, noticed a change in her husband’s skin odor 12 years before he was diagnosed with Parkinson’s disease. Later, her incredible olfactory abilities were put to the test in clinical trials, which revealed that she could detect particular molecules in the sebum produced by Parkinson’s disease. She reported that when she worked as a nurse, cancer patients had a unique scent to her.
In 2018, he visited a cancer-sniffing dog training center to test his own skills by sniffing out masks that cancer patients and healthy people had breathed into. The results were very promising and she correctly identified who most of the masks belonged to. However, some sources claim that the odors detected by humans are likely not the odor of cancer directly, but symptoms or side effects of treatment. It looks like the jury may still be out.
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